1. Field of the Invention
The invention relates to a monolithically integrated microcomputer being clocked at a processor clock rate, including a central processing unit and at least one functional unit operating asynchronously with the processor clock rate and being controlled by a clock generator that is synchronizable by external signals, the clock generator being in the form of an RC oscillator.
2. Description of the Related Art
Such a computer is needed if it is not only to perform the usual functions of a microcomputer, but also to incorporate text and graphics into an RGB video signal, such as a television picture. Microcomputers which are known for such a purpose use an RC oscillator, with an integrated Schmitt trigger but an externally wired frequency-determining capacitor and feedback resistor. A multivibrator having an inverting Schmitt trigger is known, among other sources, from the book Halbleiter-Schaltungstechnik ASemiconductor CircuitryU, by U. Tietze and C. Schenk, 8th Ed., 1986, page 177, FIG. 8.31, and the description of that figure. The output of an inverting Schmitt trigger therein forms the output of the oscillator and is fed back to the input of the Schmitt trigger through a frequency-determining resistor. The input of the Schmitt trigger is also connected through a frequency-determining capacitor to a ground potential.